The present invention relates to an electrical connection system for a vehicle which includes a high-voltage battery supplying higher voltage than that required for driving vehicle load in the vehicle. This system converts electrical power from a high-voltage battery and supplies it to handle the vehicle power load.
In recent years, a development is pursued to enhance fuel economy. According to this development, high-voltage power source of 42V is connected to a motor generator. This power source drives various vehicle loads mounted in an automobile.
This high-voltage power source is mounted in an in-car multiplex communication system. This system includes a signal line wired in the vehicle and a power source line. In this system, each ECU (Electrical Control Unit) controls the vehicle load provided in each portion of the vehicle. Each ECU requires a low-voltage power source as low as 5V.
As disclosed in Japanese Patent Application Laid-open No.H10-84626, when high-voltage from the high-voltage power source is converted into low-voltage in this system, the high-voltage is collectively converted using a DC/DC converter in a junction box, and electricality is distributed to each ECUs.
In the electricity distributing method, however, when failure of ECU or the like causes for short-circuit between a low-voltage circuit which is activated by low voltage and a high-voltage circuit which transmits high voltage, high voltage is applied to every low-voltage circuit including a plurality of ECUs. With this application of voltage, normally activating ECUs or output side of the DC/DC converter in the junction box are brought into overvoltage state.
Even when a fuse is inserted into the junction box and a low-voltage electrical wire between ECUs, high voltage is adversely applied to the low-voltage circuit unless current which blows out the fuse flows.
According to the conventional system, if a failure is caused in a single ECU out of a plurality of ECUs connected to each other, there is an adverse possibility that this failure interfere with all the low-voltage circuits.
The present invention designs an electrical connection system for a vehicle. With this system, even if a failure is caused in a single vehicle load out of a plurality of vehicle loads handling different voltage, other vehicle loads can reliably be protected.
The first aspect of the invention is directed to an electrical connection system for a vehicle. The system includes: a voltage converter including an input terminal connected to a first power supply line to supply a first voltage for converting the first voltage into a second voltage to be output to first vehicle-mounted loads through a second power supply line. The system includes a first voltage supplier branched from the first power supply line for supplying the first voltage to each of second vehicle-mounted loads. The system includes fuses provided respectively to the second vehicle-mounted loads between the voltage converter and each of the second vehicle-mounted loads on the second power supply line;
a switch provided between the voltage converter and the fuses, with a terminal connected to the second power supply line, and with another terminal connected to a ground terminal. The system includes a voltage detector provided between the voltage converter and the fuses for detecting a voltage to be supplied to the second power supply line. The system includes an overvoltage protector configured to turn on the switch to connect the second power supply line to the ground terminal, when the overvoltage protector decides an overvoltage to occur on the second power supply line due to occurring a short circuit between the first power supply line and the second power supply line at a vehicle-mounted, load, based on a voltage to be detected by the voltage detector.
Preferably, the second vehicle-mounted loads include electrical control units (ECU) for controlling vehicle-mounted electrical components.
Preferably, the fuses are adapted for the first voltage.
The second aspect of the invention is directed to an electrical connection system. The system includes a power source circuit for outputting a first voltage to operate a first load circuit. The power source circuit includes a conversion circuit for converting the first voltage into a second voltage lower than the first voltage. The system includes a second load circuit operative in response to the second voltage. The system includes a protection circuit for shunting the current from the second load circuit when a threshold voltage in the second load circuit exceeds a maximum rated voltage of the second load circuit that is between the first voltage and second voltage. The threshold voltage affects the second load circuit in substantially the same way as when the first voltage is applied to the second load circuit.
Preferably, the protection circuit includes a switch connected to the second load circuit.
Preferably, the protection circuit includes a controller for comparing the second load circuit with the threshold voltage to output a signal for closing the switch.
Preferably, the first and second load circuits include an electrical component connected thereto, for activating by the second voltage to control the first voltage.
Preferably, the second load circuit includes an overcurrent device connected to the electrical component.